No description available.

No description available.

A forced choice reaction time (RT) task was used to assess developmental changes in filtering and the related ability to narrow the focus of the attentional lens among persons with autism as compared to a group of typically developing children matched on different standardized measures. The participants included 35 persons with autism (CAs between 8.3 and 13.2 years, M = 9.8 years) and 35 typically developing children (CAs between 4.8 and 7.3 years, M = 5.9 years) between the mental ages (MA) of 5 and 8 years. The measures used for matching include the Leiter International Performance Scale - Revised (Leiter-R; Roid and Miller, 1997), the Peabody Picture Vocabulary Test - Third Edition (PPVT-III; Dunn and Dunn, 1997), and the Expressive One Word Vocabulary Test (EOWVT; Gardner, 1990). The conditions varied with regard to the presence or absence of distractors, their proximity (none, close, and far) to a target stimulus, and the presence or absence of a visual window within which the target stimulus was presented. (Abstract shortened by UMI.)

A forced choice reaction time (RT) task was used to examine the relations between covert orienting (shifts in attention independent of eye movement) and filtering (the inhibition of processing of irrelevant stimuli) components of attention in persons with autism (n = 12) and developmentally disabled persons without autism (n = 20). Conditions varied with regard to the validity of the cue (related to covert orienting) and presence of distractors (related to filtering). ?'he RT/p(correct) scores of both groups were longer in the distractor-present conditions and in conditions when a cue provided incorrect information regarding the location of the subsequent target (invalid cue). The RT/p(correct) scores of persons with autism as compared to developmentally disabled persons without autism were slower overall. However the pattern of performance of persons with autism was not significantly different from that of the developmentally disabled persons without autism. These results are inconsistent with the notions of specific deficits in covert orienting and filtering among persons with autism and indicate that certain attentional difficulties may not be unique to autism. Alternatively, they may also reflect differences in the specific mechanisms assessed in different studies. Findings are discussed in terms of the specificity of visual filtering and covert orienting impairments in autism.

Selective attention involves focusing on one event among many, and is largely responsible for an organism's ability to respond efficiently to the environment. The location at which attention is focused is a function of an ongoing tension between external cues and internal goals. Control over selective attention is often described as an executive process, attributable to the function of the frontal lobes of the brain. The present experiments investigated the role of the frontal cortex in attentional control, through the study of patients with focal cortical lesions and through functional neuroimaging in neurologically normal subjects. It was found that patients with unilateral surgical resections from the frontal cortex were as efficient as patients with temporal-lobe resections and normal controls at attending selectively to a visual stimulus at one location in the presence of irrelevant distracting stimuli. In fact, those patients whose lesions invaded the anterior cingulate gyrus tended to be less reactive to changes in irrelevant stimuli. However, patients with frontal cortex lesions were mildly impaired in a different task in which they used visual cues to direct attention voluntarily to a different location from one trial to the next. In addition, patients with excisions from the right frontal cortex performed less efficiently with increasing time spent on a task, suggesting an important role for this region in sustained attention. These observations prompted a further study of attention using positron emission tomography in normal subjects. This experiment was designed to identify the brain regions that were more active during trials in which cues could be used to direct attention voluntarily, relative to trials in which uninformative cues were presented. The striatum and extrastriate cortex were the only regions in which blood flow correlated positively with the proportion of trials containing informative cues. The present studies indicate that the frontal

The purposes of the study were to (1) determine the correlation of visual-motor performance (as measured by a visual-motor integration test and writing assessment) with achievement scores in reading skills and spelling, and (2) to examine the possible effectiveness of using paper-pencil motor training as a means of aiding the development of perceptual-motor, handwriting, and reading skills.At the beginning of the school year, 76 first grade children in four classes in one school were given the following tests: the-Beery and Buktenica Developmental Test of Visual-Motor Integration, Metropolitan Achievement Tests, Primer Level, "Part 1: Listening for Sounds," and "Part 2: Reading" (items 1-28), and a handwriting test. Near the end of the academic year, in May, the copying children were given the same tests with the addition of five items on the Reading subtest, and a spelling test taken from the vocabulary of the Ginn series, Reading 360 Performance scores were used for within-group correlations of the variables and for comparisons of class achievement.Two of the classes received no special instruction in visual-motor perception. One experimental class was instructed with the Frostig Developmental Program in, Visual Perception, Pictures and Patterns, which uses geometric forms or drawings of objects for practice in perception, while the other experimental class utilized a program specifically designed for this study which employs alphabet and word-forms presented with the same worksheet format.Analysis of the data indicated that the observed within-group correlation of pretest scores of visual-motor integration and writing was significant at .40 (above .23 necessary to be statistically significant from zero). Visual-motor performance correlated significantly with listening for sounds (.28), but not with reading (.14). Correlations of pretest writing and reading skills were significant, .57 with listening for sounds, and .48 with reading as measured by the Metropolitan tests.In contrast with pretest results, the within-group correlations of posttest scores for the variables showed a very low correlation of VMI with writing (.12), and a lower correlation of writing with reading skills (.28 for both Metropolitan subtests). Correlation of VMI and reading skills showed a minimal significant correlation of .23 with reading, and .31 with sounds which was higher than the relationship noted in pretest score correlations.Correlation of pretest scores with posttest results was suggested for possible predictive use. The correlation of pretest writing with posttest listening for sounds (.42), with reading (.58) and spelling (.58) indicated that this comparison might be worthy of consideration for further investigation.To determine the effectiveness of visual-motor training a comparison was made of the four treatment groups using the pretest and posttest scores of performance on the visual-motor, writing, listening for sounds, and reading tests. In order to establish that the pretest scores of the classes were not significantly different and that the classes were equivalent, a multivariate and univariate analysis of variance with treatment for sex differences was made. The results indicated that the four treatment groups were not significantly different on the variables tested except for one measure of writing which was therefore not included in. the posttest analysis.The null hypothesis that there is no statistically significant difference between the vectors of mean posttest scores of children receiving perceptual-motor training and those who did not was not rejected, (F4 68 = .5193; p (.72). It was also concluded that there was no statistically significant difference between the performances of the two experimental groups, (F4,68 = .6408, p < .63); there was no statistically significant difference in the scores of performance of the two comparison groups, (F4 68 = .88, p < .4779).Although development of visual-motor perception may be important as a componentof growth and learning, the results of this study do not show significant correlation with reading achievement in first grade. Significant differences were not disclosed in two different approaches to perceptual motor development, one employing geometric forms, and the other alphabet letter symbols.

A model of stereopsis is proposed in which information from each eye's image is organised as a scale-based hierarchy before binocular comparison. The algorithm incorporates coarse-to-fine matching (like Marr and Poggio, 1979) but differs from previous models in that the position, and hence disparity, of features is defined relatively rather than by their retinal co-ordinate. Thus, fine scale disparities are measured and recorded relative to coarse scale disparities. Local surface slant and curvature is represented explicitly at a range of spatial scales. The theory is based on a hierarchical model of encoding position (Watt, 1988). The first experiment investigates the time course of shape discrimination in random dot stereograms. The results are compatible with a model in which the scale of analysis changes from coarse to fine over the first second of viewing. The second experiment measures the magnitude of a new "3-D" Müller-Lyer illusion and compares it to that of the classical (2-D) illusion. Both these and the cyclopean Müller-Lyer illusion are consistent with a model in which hierarchical encoding of position is used by the visual system for 2-D (length comparison) and 3-D (slant) judgements. The third experiment compares the detection of large disparities and large displacements. "D_max" for the motion and stereo tasks is shown to be similar over a wide range of dot densities. The results are interpreted as evidence that similar spatial primitives are used in the correspondence process in both domains. The spacing of MIRAGE centroids (Watt and Morgan, 1985) fit the data well. The proposed hierarchical model is similar to that put forward by Mitchison and McKee (1987), although their scheme was not based on spatial scale. The model bridges the gap between a primal and a 2 1/2-D sketch (Marr, 1982) and has important implications for many issues within stereopsis.

No description available.

Attentional orienting involves two neuroanatomically and functionally separate components, the reflexive and voluntary attentional sub-systems, which interact to orient attention on the environment. Three experiments, in which a cueing paradigm was used, examined reflexive and voluntary orienting over later childhood development (i.e., 8--14 years old) in order to explore the mechanisms underlying the development of the control of attentional orienting. Experiments 1 and 2 explored whether reflexive and voluntary orienting develop in parallel, and examined the influence of cue predictability on attentional orienting during development. Experiment 3 explored the role of explicit instructions in the influence of cue predictability on voluntary and reflexive orienting. The results indicate that the development of attentional orienting over later childhood is a reflection of the operation of an underlying mechanism, general developmental changes in speed of processing. Apart from this mechanism, the efficiency of attentional orienting remains the same across age. In addition, the influence of cue predictability on attentional orienting reflects the operation of a low-level mechanism which operates independently of strategic influences; this mechanism may be covariance detection and judgment. The implications of these conclusions for modeling attentional orienting, and the development thereof, are considered.

Previous studies show that recovering alcoholics exhibit deficits in perceiving facial affect. The present study investigates whether these deficits are present prior to the onset of alcoholism. Participants with a family history of alcoholism (FHP) and participants without such a family history (FHN) selected the emotion label they felt most closely corresponded with stimuli viewed on a computer screen. Zuckerman's Sensation Seeking Survey was also completed. The data revealed a relationship between family history of alcoholism and the perception of facial expressions. Additionally, FHP participants were higher in sensation seeking compared to FHN participants and high sensation seekers were less accurate in categorizing fearful expressions. Disinhibition and boredom susceptibility were identified as the traits driving the effect between sensation seeking and fear categorization accuracy. An account of how these traits may be associated with both decreased fear perception and a greater risk for alcoholism is discussed, and future research directions suggested.